Brussels sproutsBrassica oleracea var. gemmifera

Brussels sprouts occupy the ground from June to February and grow up to a metre tall: choose a bed you can leave to them all season, in full sun, and preferably sheltered from the westerly winds that flatten them in winter. They like heavy, deep, well-structured soils, where they anchor firmly; our clays and loams suit them wonderfully, sandy soils less so. Keep a rotation of four to five years without brassicas and avoid the immediate company of strawberries and tomatoes. The spot where peas or broad beans were pulled up in June is ideal.

This is the cabbage that fears excess manure the most: in freshly manured soil, it produces loose, open sprouts that fall apart. So manure the previous autumn, three to four kilos of mature compost per square metre, worked in to twenty-five centimetres, or plant it on a bed already manured for a previous hungry crop. Lime lightly on acid soil. In spring, do not dig: scratch the surface, remove weeds and above all firm the soil with a roller or the rake. Firm soil gives sturdy stems and tight sprouts; fluffed-up soil, the opposite.

Sow in an outdoor seedbed from late March to late April, under insect-proof mesh, in rows ten centimetres apart, one seed every two centimetres, one centimetre deep. A March sowing under a cold frame is possible for early varieties, but a sowing under heated cover gives drawn plants best avoided. Do not sow after mid-May: the plant would no longer have time to form its sprouts before winter. Choose a late, hardy variety, Groninger, Sanda or Brilliant, for a harvest from November to February, when Brussels sprouts are truly at their best.

Thin to five centimetres as soon as the seedlings are up or prick out into eight-centimetre pots at the two-true-leaf stage. A plant ready to set out is six to seven weeks old, with five or six leaves and a short, robust stem. Water the seedbed regularly, never letting it dry out, and keep the mesh on until planting against flea beetles and the cabbage root fly. If the plants become leggy for lack of light or space, they will give thin stems unable to carry the sprouts in winter. A module-grown plant from a garden centre, bought in May, is a good fallback, provided it is stocky and dark green.

Set out from mid-May to late June, in overcast weather, spacing sixty to seventy centimetres each way. Dig a hole with a trowel, bury the plant up to the first leaves and firm hard around the stem, with your fist then your heel: this is the most important operation of the whole crop. The plant must resist a firm tug on a leaf. Water three litres per plant into a basin. Fit a cardboard collar against the cabbage root fly, then insect-proof mesh over tall hoops, or a fine-mesh net, until the end of September.

Brussels sprouts are not a window-box vegetable, but they grow in a container of forty litres and forty-five centimetres deep, filled with heavy potting compost mixed with garden soil and a third of garden compost, very well firmed. Choose a dwarf variety such as Rubine or Long Island. Place the container in the sun, against a wall to shelter it from wind, stake from July, water every day in summer and feed with plant liquid every three weeks until August. There will be fewer sprouts, but a container on a Brussels terrace, harvested under the frost, has its charm.

Planting in loose, freshly manured soil, without firming, is the main cause of open, unusable Brussels sprouts. Planting too early, in April, in rich soil, produces an enormous plant that forms its sprouts in September, in mild weather, and watches them blow open. Planting too close, at forty centimetres, deprives the stems of air and light. Neglecting to stake in a windy spot flattens the plants in November and rots the sprouts in contact with the soil. Finally, harvesting before the first frosts forgoes the sweetness that only the cold brings to the little sprouts.

Water every two or three days for the two weeks following planting, then ten to fifteen litres per square metre once a week in July-August in dry weather, at the base and in the morning. A good supply of water in summer lets the plant build its stem and foliage before the sprouts form. From September, cut back, and stop watering altogether from October: end-of-season moisture combined with mild weather gives loose sprouts. The mulch laid in July is enough to keep the soil cool.

Mulch a month after planting, six to eight centimetres of straw or dried grass clippings, keeping the collar clear. Feed in moderation: a single watering of nettle liquid diluted to 10 % in July, possibly a second in early August, then nothing more. Any late feeding, in September, produces open sprouts and soft stems that stand up badly to frost. A handful of sieved wood ash at the base in August provides the potash that hardens the tissues and improves winter hardiness. If the lower leaves yellow in summer, that is normal; remove them.

Earth up the base of the stems to ten centimetres in July, then again in September: the plant anchors itself, puts out roots and resists wind. In an exposed position, put in a sturdy stake of one metre twenty from July, and tie the stem loosely at two heights. Remove yellow leaves from the base through the season, snapping them downwards, to give the sprouts air. Around late September or early October, when the lowest sprouts are the size of a hazelnut, cut the top off the plant: the sprouts then swell all together and faster. Do not do this on very late varieties, which are harvested in February.

Mealy cabbage aphids are the real scourge of Brussels sprouts: they lodge in the forming sprouts from August. Hose them off in the morning, spray soft soap diluted to 5 % every five days in an attack, remove heavily infested sprouts, and let dill or coriander flower nearby to attract hoverflies and ladybirds. The cabbage white is kept at bay under mesh until September. Whitefly settles under the leaves in summer: a jet of water and removal of the lower leaves. The cabbage root fly is prevented by the collar. Pigeons call for a net from December.

In April, sow in a seedbed under mesh. In May, prick out into pots, then plant in late May, firming hard, collar and mesh. In June, water, hunt slugs. In July, mulch, earth up, stake, feed once. In August, ash at the base, watch for aphids and cabbage white, remove yellow leaves. In September, earth up again, stop watering, remove the mesh at the end of the month, top the plants. In October, wait for the first frost. From November to February, harvest from the bottom up, net against pigeons. In March, pull up the stems and dispose of them; they compost badly.

Wait for the first proper frost, often in early November, before harvesting: the cold turns starch into sugar and sweetens the sprouts. Pick from the bottom up, with a downward push of the thumb or with a knife, when the sprouts are firm and the size of a walnut, removing the corresponding leaf. Take from several plants at a time rather than stripping a single stem. The sprouts hold in the ground all winter, even under snow. In February, when the last sprouts open up, harvest the leafy young shoots at the top, as tender as spring greens. A whole cut stem keeps for two weeks in a cellar.